Electronic locking circuit



w. A. MILLER 2,631,231

March 10, 1953 ELECTRONIC LOCKING CIRCUIT Filed May 25, 1950 POTENT/HL 47' 14/9 00! 0/ .10 7

pd7i/v77iL 147' 14/9905 0F 20 60 INVENTOR WILLIAM A.MILLEH ATTORI JEY Patented Mar. 10, 1953 2,631,231 ELECTRONIC LOCKING CIRCUIT William A. Miller, Port Jefi'erson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application May 25, 1950, Serial N 0. 164,078

Claims. 1

This invention relates to triggercircuits. More particularly the present invention is an improvement in trigger or locking circuits of the type having two discharge tubes which are made conductive alternately.

In many applications of electronic locking, or trigger circuits it is desirable that the output voltage be clamped to a reference potential or have one extremity of the waveform always return to the, same reference potential. D. C. restorers or clamping circuits are used to perform this function. Much additional complex circuitry is required in the event it is desired to make the reference potential to which the waveform is clamped, a variable one. In a copending application for a Multivibrator Circuit, filed May 25, 1950, Serial No. 164,077, now Patent No. 2,603,751, issued July 15, 1952, there is described and claimed a multivibrator circuit which provides an output which is automatically clamped to a reference potential.

It is an object of the present invention to provide an improved trigger circuit'having an output which is automatically clamped to a reference potential.

It is another object of the present invention to provide an improved trigger circuit having an output which is automatically clamped to a reference potential which is adjustable.

It is still another object of the presentinvention to provide an improved trigger circuit. having an output which eliminates therequirement for clamping circuits.

These and further objects of the present invention are achieved by providing a two-tube trigger circuit having cross-connected anodes and grids wherein a first one of the tubes has its anode connected to the B+ power supply through a load resistor, and its cathode grounded. The second one of the tubes has its cathode and grid connected to a negative source of power and bias and its anode connected to ground through an anode load resistance. The output from the anode, which is coupled to ground; varies from ground potential to a value which is negative with reference to ground potential. Thev value of the clamping or reference potential may be controlled, in some degree by using a potene tiometer to supply a suitable potential to the anode of the second tube.

v The novel features of the invention, as well as the invention itself, both as to its organization and method of operati0n, will best be understood from the following description, when read in connection with the. accompanying drawings, in which- Figure 1' is a circuitdiagram-of an embodiment of the invention,

Figure 2 is agraphical representation ofthewave-shapes of the output available from the circuit shown in Figure 1, and

Figure 3 is a circuit diagram of a modification of" the embodiment of the invention shown Figure. 1'.

Referring'now'to Figure 1, afirst electron dis charge tube has an anode I2 connected to the grid 2 of a: second electron discharge tube 20'' through a resistor 2|. The grid M of the first electron discharge tube I0 is directly connectedto the anode 22 of the second electron discharge tube 29. Each tube has an individual load resistor I8; 28. A source of operating potential 30 is provided having a reference potential point or ground 32', also a positive terminal 34 and first and second negative" terminals 36, 38. The positive terminal 34 is positive with reference to ground 32 and both negative terminals 36, 33 are negative with reference to ground, the second negative terminal 38 being more. negative: than the first 36.

One of the load resistors 18 connects the positive terminal 34 to the first tube anode I2. The other of the load resistors 28 connects ground orthe point of reference potential 32 to the anode 22; of the second tube 20. The first tube cathode is is connected to ground. The second" tube cathode 28is connected to the first negativete'r minal' 36. A grid leak resistor 40 connects the grid 24 of the secondt'ube 20 to the second negative terminal-38; Two condensers 42', are used to connect each of the grids M, 24 to an isolating rectifier 46. The isolating rectifier 46' is connected to the" signal input terminals? through a condenser 50. The isolating? rectifier 46' is used to isolate the trigger circuitfrom a signal generating circuit; Output is obtained from the second tubeanode 22by means of output terminals 54 which are connectedt'o' this anode: and ground;

For the purpose of description oftheoperation' ofthe trigger circuit shown in Figure 1, it'is" assumedthat the first tube" is conducting. The voltage at its anode, l2, accordingly; is low. The voltage applied therefrom to the grid Zloftlie second tube, together with the bias from the second negative terminal 38, renders the grid 24 sufii'ciently negative with reference to the second tube cathode 26 to maintain the second tube 20 non-conducting. This is obtained by proper choice of the coupling. resistor 2|, the gridleak' resistor, 40, and the potential of the: second", negative terminal'38; A'negative'pulse applied to first tube grid I4, is of sufficient amplitude, the

first tube is made to go to cutoff. The anode potential of the first tube accordingly rises. Thi rise in potential is communicated to the second tube grid 24 and causes the second tube 20 to become conductive, if the proper selection of resistance values has been made. The anode 22 of the second tube, accordingly, is swung from ground potential, when the second tube is not conducting, to some negative value, when it is conducting. This negative value is dependent on the current which the tube can pass and the negative bias applied to the cthode 26. This second tube anode negative potential is directly applied to the grid M of the first tube to maintain it at cutofi.

The trigger circuit maintains this stable condition until a second negative pulse is received. This causes the second tube to be driven to cutoff. When the potential applied to the grid of the first tube rises accordingly, the first tube commences current conduction. This allows the grid 24 of the second tube to remain at cutoif since the anode potential of the first tube drops when the tube becomes conductive. The trigger circuit maintains this stable state until another negative pulse is received. If desired, a small capacitance may be shunted across the coupling resistor to speed up the tube conduction change-over.

Referring to Figure 2, there may be seen graphical representations of the voltage waveshapes available at the anodes of the first and second tubes responsive to signal pulses which trip the trigger circuit. The first tube anode voltage is substantially rectangular and above ground potential. The second tube anode voltage is also substantially rectangular and varies from ground potential, when the tube is not conducting, to' a negative value, when the tube is conducting. It may therefore be seen that the second tube output is clamped to ground or a referencepotential. In view of the ground potential connection, the anode of the second tube may be connected directly to succeeding apparatus without the usual coupling condenser required to block out anode D. C. potential. No D. C. restoration or clamping is required for an output taken from the anode of the second tube.

Figure 3 is a circuit diagram of a modification of Figure 1. Similar functioning parts of Figure 3 are identified by similar reference numerals. The modification consists of a potentiometer 56 having its fixed resistance 58 connected across the power supply 30 in a manner to range from positive to negative and to values of potential and includes the point of reference potential 32. This may be done by tapping the potential source, as shown, using supplementary dropping resistors, or in any other manner which is well known to the art. The arm Bl! of the potentiometer 56. which is in slidable contact with its fixed resistance .58 is connected to the anode load resistor 28 of the second tube 20.

Movement of the potentiometer slidable arm 60 permits application of potentials from a positive value through zero to a negative value. The effect of these variationschanges the level to which the output from the second tube anode rises and therefore afiords a. means for making,

as desired, the clamping level positive or negative with respect to ground. The excursion of the clamping level in the positive direction, however, is considerably limited by the condition of cutoif 0f the first tube. Although the subject trigger circuit is described and illustrated using triodes, multigrid tubes are equally effective.

From the foregoing description it will be readily apparent that there has been provided an improved locking circuit having two stable conditions and having an output which is automatically clamped to a reference potential which may be varied as desired. Although a singl embodiment and modification of the present invention has been shown and described, it should be apparent that many changes may be made in the particular embodiment herein disclosed and that many other embodiments are possible, all within the spirit and scope of the present invention. It is desired, therefore, that the foregoing description shall be taken as illustrative and not as limiting.

What is claimed is:

1. An electronic locking circuit comprising a first and a second electron discharge tube each having an anode, cathode and grid, the grid of said first tube being directly connected to the anode of said second tube, the grid of said second tube being coupled to the anode of said first tube,

a first load impedance connected at one end to said first tube anode, a second load impedance connected at one end to said second tube anode, a source of operating potential, a point of reference potential, said first tube cathode being connected to said point of reference potential, means to apply a potential which is positive with respect to said point of refrence potential to the other end of said first load impedance, means to apply a potential to the cathode of said second tube which is negative with respect to said reference potential point, a grid leak resistor having one end connected to said second tube grid, means to apply. a potential to said grid leak resistor which is more negative than said negative potential apimpedance and means to vary as desired the value said first tube being directly connected to the anode of said second tube, the grid of said second tube being coupled to the anode of said first tube, a first load impedance connected at one end to said first tube anode, a second load impedance connected at one end to said second tube anode, a source of operating potential, a point of reference potentiaL'means to connect said first tube cathode to said point of reference potential, means coupling the other end of said second load impedance to said point of reference potential, means to apply a potential which is positive with respect to said reference potential to the other end of said first load impedance, means to apply a potential to the cathode of said second tube which is negative with respect to said reference potential, a grid leak resistor having one end connected to said second tube grid, means to ap-' and second tubes, and means to derive an output from said second tube anode.

3. A trigger circuit comprising a first and a second electron discharge tube each having an anode, cathode and grid, the grid of said first tube bein directly connected to the anode of said second tube, the gridof said second tube being coupled to the anode of said first tube, a first load impedance connected at one end to said first tube anode, a second load impedance connected to said second tube anode, a source of operating potential, a point of reference potential, said first tube cathode being connected to said point of reference potential, means to apply a potenial which is positive with respect to said point of reference potential to the other end of said first load impedance, means to apply a potential to the cathode of said second tube which is negative with respect to said reference potential point, a grid leak resistor having one end connected to said second tube grid, means to apply a potential to said grid leak resistor which is more negative than said negative potential applied to said second tube cathode, a potentiometer including a fixed impedance and an arm slidably in contact with said impedance, said slidable arm being connected to'the other end of said second load impedance, means to apply a potential which is positive with respect to said reference potential point to one end of said potentiometer fixed impedance, and means to apply a potential which is negative with respect to said reference potential point to the other end of said potentiometer fixed impedance.

4. A trigger circuit having two stable states comprising a first and a second electron discharge tube eachhaving an anode, cathode and grid, the grid of said first tube being directly connected to the anode of said second tube, a resistor coupling said second tube grid and said first tube anode, a first load resistor connected at one end to said first tube anode, a second load resistor connected at one end to said second tube anode, a source of operating potential including a point of reference potential, a positive terminal which is more positive than said point of reference potential, a first negative terminal which is more negative than said point of reference potential and a second negative terminal which is more negative than said first negative terminal, the other end of said first load resistor being connected to said positive terminal. said first tube cathode and said second resistor other end being connected to said point of reference potential. said second tube cathode being connected to said first negative terminal, a grid leak resistor connecting said second tube grid and said second negative terminal, means to apply tripping pulses to the grids of said first and second tubes, and means to derive an output from said second tube anode.

5. A trigger circuit having two stable states comprising a first and a second electron discharge tube each having an anode, cathode and grid, the grid of said first tube being directly connected to the anode of said second tube, a resistor coupling said second tube grid and said first tube anode, a first load resistor connected at one end to said first tube anode, a second load resistor connected at one end to said second tube anode, a source of operating potential including a point of reference potential, a positive terminal which is more positive than said point of reference potential, a first negative terminal which is more negative than said point of reference potential and a second negative terminal which is more negative than said first negative terminal, the other end of said first load resistor being connected to said positive terminal, said first tube cathode being connected to said point of reference potential, said second tube cathode being connected to said first negative terminal, and a grid leak resistor connecting said second tube grid and said second negative terminal, a potentiometer including a fixed resistance and an arm slidably in contact with said fixed resistance, means to couple said potentiometer fixed resistance between said positive and first negative terminal to provide a range of potentials along said fixed resistance including said reference potential, the other end of said second load resistor being connected to said potentiometer slidable arm, means to apply externally derived signals to the grids of said first and second tubes, and means to derive an output from said second tube anode.

, WILLIAM A. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,159,792 Geiger May 23, 1939 2,441,006 Canfora May 4, 1948 

